1. Field of the Invention
The present invention relates to a conductive rubber member suitable for use in an image-forming apparatus such as an electrophotographic copying machine or printer or a toner-jet copying machine or printer, and more particularly to a conductive rubber member suitable for a conductive roller, blade, belt, etc.
2. Background Art
Conductive rollers employed in an image-forming apparatus such as an electrophotographic copying machine or printer are required to have satisfactory conductivity and not stain a member such as a photoreceptor. Therefore, conventionally, such rollers have been made of polyurethane or silicone rubber Japanese Patent Application Laid-Open (kokai) Nos. 6-175470 (Claims, etc.), 5-281831 (Claims, etc.), 4-214579 (Claim 2, [0022], etc.), 2002-040760 (Claims, etc.), among other documents, disclose improved conductive rollers in which a coating layer or a surface-treated layer is provided on the surface of an elastic layer, or a coating tube is fitted to conductive rollers.
The present applicant previously developed a charge-imparting member which can be produced at low cost and which maintains excellent performance for a long period of time, and filed an application (see Japanese Patent Application Laid-Open (kokai) No. 2002-040760 (Claims, etc.)). The disclosed charge-imparting member has an elastic layer formed of an epichlorohydrin-based rubber material, and a surface-treated layer which has been formed through treating the surface of the elastic layer with a surface-treatment liquid containing a conductivity-imparting agent, at least one species selected from an acrylic fluoropolymer and an acrylic silicone polymer, and an isocyanate component.
The conductive roller disclosed in Japanese Patent Application Laid-Open (kokai) No. 2002-040760 is produced by use of a surface-treatment liquid containing a conductivity-imparting agent such as carbon black. Although the roller is imparted with conductivity, electrical resistance of the roller tends to vary in accordance with the dispersion state of carbon black, which is problematic.
When a conducting agent other than carbon black is used, properties of the roller are largely affected by environmental factors, failing to attain consistent image formation, which is also problematic.
The present applicant also developed a conductive rubber member and disclosed such a member in Japanese Patent Application Laid-Open (kokai) No. 2007-31703 (see Claims, etc.). The disclosed conductive rubber member has a surface-treated layer which has been produced through impregnating the surface portion of the rubber member with a surface-treatment liquid containing an ion-conductivity-imparting agent and a thermosetting compound dissolved in a solvent, followed by thermosetting. The conductive rubber member is less affected by environmental factors and exhibits stable electrical resistance. However, when used under severe working conditions, the rubber member tends to exhibit large variation in electrical resistance.